Strength training device



FIG. 1 is a perspective view of a strength training device showing our new design;

FIG. 2 is a front view of the strength training device, the back view being identical to the front view;

FIG. 3 is a top view of the strength training device, the bottom view being identical to the top view; and,

FIG. 4 is a side view of the strength training device.

The broken lines illustrate portions of the strength training device which form no part of the claimed design. 

The ornamental design for a strength training device, as shown and described. 